1. Field of the Invention
This invention relates to a zero net external displacement implantable pump and driver intended primarily for use in connection with an implantable anti-reflux fluid displacement peritoneovenous shunt used to transfer an unwanted accumulation of body fluids from a body cavity to a site where it can be processed by the body. The primary use for the shunt is in the treatment of patients with ascites by the displacement of accumulated peritoneal cavity fluid into the systemic venous circulation.
This application is related to Buchwald et al U.S. Pat. No. 4,657,530, issued Apr. 14, 1987, entitled Compression Pump-Catheter and directed to a manually operable ascites shunt. The device of the aforesaid patent is a peritoneovenous shunt in which ascites fluid is transferred from the peritoneum to the vasculature via a manually operated compression pump. That device is not a viable alternative for certain patients who require peritoneovenous shunting but for a variety of reasons are unable to perform the pumping mechanics.
To operate such a manually compressible pump implanted within the body by compression of the body surface over the pump, there must be some net displacement of volume. This displacement can take place within the pump in which case there must be adequate internal pressure resisting the applied pressure to return the pump to its original state for the next stroke. This internal pressure, supplied by spring action, must be great enough to expand the overlaying tissue to its original position as well as provide all the negative pressure for the pump intake stroke. During the compression stroke of the pump, one must therefore provide the summation of the output back pressure and the spring compression force for the inlet suction as well as some excess pressure to insure that the tissue deformation force is overcome. The pump according to the present invention reduces the force needed for operation by using a two stroke dual action pump that has zero net external displacement.
2. The Prior Art
No pertinent prior art is known.